spawnSync: do not forward SIGPWR on Linux

src/jsc/bindings/c-bindings.cpp

@@ -933,10 +933,12 @@
     M(SIGIO);
 
 #if OS(LINUX)
+// SIGPWR is intentionally excluded: JSC uses it for GC thread suspend/resume
+// (see WTF/wtf/posix/ThreadingPOSIX.cpp). Replacing its handler can terminate
+// the process when the GC next signals a thread.
 #define FOR_EACH_LINUX_ONLY_SIGNAL(M) \
     M(SIGPOLL);                       \
-    M(SIGPWR);                        \
     M(SIGSTKFLT);
 
 #endif
 

test/js/bun/spawn/spawnSync-sigpwr-gc.test.ts

@@ -0,0 +1,58 @@
+import { expect, test } from "bun:test";
+import { bunEnv, bunExe, tempDir, isLinux } from "harness";
+import { join } from "path";
+import { symlinkSync } from "fs";
+
+// Regression: spawnSync's signal-forwarding list included SIGPWR on Linux.
+// JSC uses SIGPWR to suspend/resume threads for GC. Bun.openInEditor spawns a
+// detached thread per call that runs spawnSync; concurrent calls race on the
+// process-wide previous-handler table and can leave SIGPWR at SIG_DFL. The
+// next GC suspend then terminates the process with signal 30.
+test.skipIf(!isLinux)(
+  "spawnSync signal forwarding does not clobber JSC's SIGPWR handler",
+  async () => {
+    const sleepBin = Bun.which("sleep");
+    expect(sleepBin).toBeTruthy();
+
+    using dir = tempDir("spawnSync-sigpwr", {
+      "run.js": `
+for (let i = 0; i < 64; i++) {
+  try { Bun.openInEditor("0.2"); } catch {}
+}
+let junk = [];
+for (let i = 0; i < 2000; i++) {
+  junk.push({ a: new Uint8Array(4096).fill(i), b: { c: i } });
+}
+for (let i = 0; i < 30; i++) Bun.gc(true);
+console.log("ok");
+`,
+    });
+    // Make `code` (first in the editor preference list) resolve to `sleep`, so
+    // each background spawnSync holds its signal-forwarding window open long
+    // enough for threads to overlap.
+    symlinkSync(sleepBin!, join(String(dir), "code"));
+
+    await using proc = Bun.spawn({
+      cmd: [bunExe(), join(String(dir), "run.js")],
+      env: {
+        ...bunEnv,
+        PATH: String(dir),
+        EDITOR: "",
+        VISUAL: "",
+      },
+      stdout: "pipe",
+      stderr: "pipe",
+    });
+
+    const [stdout, stderr, exitCode] = await Promise.all([
+      proc.stdout.text(),
+      proc.stderr.text(),
+      proc.exited,
+    ]);
+
+    expect(proc.signalCode).toBeNull();
+    expect(stderr).not.toContain("AddressSanitizer");
+    expect(stdout.trim()).toBe("ok");
+    expect(exitCode).toBe(0);
+  },
+);